Measuring individual phase flow rates and other properties of a multiphase flow is challenging because phase distribution and phase velocities in the flow may vary significantly in time and space. A number of technologies have been employed and multiphase flow meters (MPFMs) are commercially available. U.S. Pat. No. 7,908,930 disclosed the use of microwave transmission and receiver antennas for measuring multiphase flow water hold-up and water liquid ratio by measuring the mixture permittivity and/or conductivity at a Venturi throat section together with an (exempt source) gamma ray mixture density measured at the same cross-section as the microwave measurements. However, the use of a gamma ray source is sometimes regarded as undesirable. Tomography using multiple electrodes has also been proposed for measuring multiphase flows, see for example WO2009/030870.
For a multiphase flow composed of gas and liquid with the liquid being a mixture of oil phase and aqueous phase, the properties which may be measured include                water in liquid ratio (WLR) which is the volume of aqueous phase in total volume of liquid and in the context of multiphase flow metering it is the ratio between the aqueous phase volume flow rate and the total liquid volume flow rate.        gas volume fraction (GVF) which is the percentage or fraction of gas volume flow rate with respect to total (gas and liquid) volume flow rate.        liquid holdup, also termed liquid fraction, defined as fraction of liquid present in a short interval of pipe (or other flow conduit). It is in effect a relative area of the pipe cross section occupied by the liquid (note that gas holdup=1−liquid holdup). Because each fluid moves at a different speed due to different gravitational forces and other factors, the liquid fraction or liquid holdup is not the same as Liquid Volume Fraction (LVF) which is the proportion of the total volume flow rate due to the liquid (note that LVF=1−GVF).        the volumetric flow rates of the gas, the oil phase and the aqueous phase.        